This invention relates to a bush type vibration isolator with an elastic body interconnected between inner and outer tubes.
In general, a vibration isolator which has an elastic body interconnected between inner and outer tubes is used for an engine mount, a cab mount or bushes of motor vehicles. The elastic body has a pair of liquid chambers which communicate with each other by a restricted passage in which liquid is contained. When vibrations occur, the liquid in one of the liquid chambers moves to the other chamber through the restricted passage and the vibrations are absorbed by the resistance to passage to the liquid.
It is possible to design this type of vibration isolator to enable the liquid pressure in the liquid chambers to be effectively changed in response to vibrations by disposing a pair liquid chambers on an opposite sides of the inner tube. In this bush type vibration isolator, however, the inner tube is generally placed eccentrically relative to the outer tube (e.g. Japanese Patent Laid-Open No. 224746/1987), the liquid chamber disposed in narrower space between the inner and outer tubes has a flat shape portion such that an elastic membranous member which forms a portion of a wall of this liquid chamber faces a side of the inner tube. Consequently, if an amplitude of vibration becomes large, this elastic membranous member contacts with the elastic body formed around disposed on a periphery of the inner tube, and durability of the elastic membranous member will inevitably reduced.